1. Field of the Invention
The present invention relates to an antenna with an integral RF circuit that can be mounted on a circuit board of a communication apparatus, an antenna module including such an antenna, and a communication apparatus including such an antenna.
2. Description of the Related Art
In recent years, reduction in the sizes of communication apparatuses such as on-vehicle communication apparatuses and portable communication apparatuses have been demanded, and thus, reduction in the sizes of antennas have also been demanded. Accordingly, surface-mount antennas, that is, chip antennas that can be mounted on a circuit board of a communication apparatus, have been actively researched and developed. In the surface-mount antennas, for example, radiation electrodes for transmitting or receiving radio waves are disposed on a dielectric base.
For example, a plurality of radiation electrodes is disposed on a dielectric base so that radio waves in a plurality of frequency bands can be transmitted or received by a single surface-mount antenna. When a plurality of radiation electrodes is disposed on the same dielectric base as described above, the dielectric constant of the dielectric base, which is a factor that contributes to reduction in size, strengthens coupling between the radiation electrodes. Thus, a large space is required between the radiation electrodes in order to ensure isolation between the radiation electrodes, leading to an increase in the size of an antenna. The increase in the size of the antenna prevents a reduction in the size of a communication apparatus.
In order to overcome the problems described above, preferred embodiments of the present invention provide an antenna with an integral RF circuit that readily facilitates reduction in the size of a communication apparatus, an antenna module including such a novel antenna, and a communication apparatus including such a novel antenna.
According to a preferred embodiment of the present invention, an antenna with an integral RF circuit includes a dielectric base, a top surface thereof being substantially flat, a plurality of radiation electrodes for one of or both transmission and reception of a radio wave, disposed on the top surface of the dielectric base and spaced from each other, an integral RF circuit having a circuit pattern and connected to at least one of the plurality of radiation electrodes conductively or via a capacitor, the FR circuit being disposed at least partially in a gap between the radiation electrodes, a concavity formed in a bottom surface of the dielectric base in a region corresponding to an area where the circuit pattern of the RF circuit is located, the concavity defining a thin portion and a thick portion in the dielectric base, the circuit pattern of the RF circuit being disposed on the thin portion of the dielectric base and the plurality of radiation electrodes being disposed on the thick portion of the dielectric base, and a ground electrode disposed on the bottom surface of the dielectric base and on an inner surface of the concavity.
The plurality of radiation electrodes preferably has different resonant frequencies from each other.
Furthermore, the plurality of radiation electrodes disposed on the top surface of the dielectric base preferably includes at least one radiation electrode dedicated for reception and at least one radiation electrode dedicated for transmission.
Furthermore, the RF circuit is preferably provided in one-to-one association with each of the plurality of radiation electrodes.
Another preferred embodiment of the present invention provides an antenna module including an antenna with the integral RF circuit described above, the antenna module being joined with a substrate with a bottom surface defining a connecting surface, a circuit conductively connected to the RF circuit of the antenna with the integral RF circuit and disposed in an area on the substrate surrounded by the concavity on the bottom surface of the antenna with the integral RF circuit, and a connecting device for conductively connecting the circuit and the RF circuit.
The connecting device may include a through hole formed in the dielectric base of the antenna with the integral RF circuit.
Alternatively, the connecting device may include a wiring pattern disposed on a side surface of the dielectric base of the antenna with an integral RF circuit.
Also alternatively, the connecting device may include a metallic pin disposed so as to penetrate through the dielectric base of the antenna with an integral RF circuit from the top surface to the bottom surface.
According to yet another preferred embodiment of the present invention, a communication apparatus includes an antenna with the integral RF circuit described above or an antenna module described above.
According to preferred embodiments of the present invention, a plurality of radiation electrodes are spaced from each other on a top surface of a dielectric base, and an integral RF circuit is arranged so as to be disposed at least partially in a gap between the radiation electrodes. Because the RF circuit is thus arranged on the dielectric base to efficiently utilize the gap between the plurality of radiation electrodes, any increase in the size of the dielectric base is prevented, and the RF circuit and the plurality of radiation electrodes can be disposed on the dielectric base.
Furthermore, because the RF circuit is disposed in the antenna, the RF circuit need not be disposed on a circuit board of a communication apparatus, allowing the circuit board to be made much smaller which allows for significant reduction in the size of the communication apparatus.
Furthermore, by providing the radiation electrodes on a thick portion of the dielectric base, the radiation electrodes resonate favorably, so that performance of transmission or reception of radio waves is greatly improved. Furthermore, by disposing a circuit pattern on a thin portion of the dielectric base, an electric field of the circuit pattern is confined, thereby greatly reducing radiation loss attributed to radiation of radio waves from the circuit pattern. Furthermore, compared with a case where a plurality of radiation electrodes is disposed on a uniformly thick dielectric base as shown in FIG. 7A, by making a portion of the dielectric base between the radiation electrodes thin with a concavity as shown in FIG. 7B, coupling between the radiation electrodes is diminished. Furthermore, another circuit can be disposed and included within the concavity.
According to preferred embodiments of the present invention, a plurality of radiation electrodes are arranged so as to be spaced from each other on a substantially flat top surface of a dielectric base, and an integral RF circuit is arranged at least partially in a gap between the radiation electrodes. Accordingly, the radiation electrodes are separated from each other by such a space where the RF circuit is located, so that isolation between the radiation electrodes is ensured. Furthermore, a portion of the dielectric base between the radiation electrodes is made thin because of the formation of the concavity, so that coupling between the radiation electrodes is minimized. This also contributes to ensure isolation between the radiation electrodes.
Furthermore, when a plurality of radiation electrodes is disposed in parallel, a gap between the radiation electrodes has conventionally been a dead space and has not been utilized. However, according to preferred embodiments of the present invention, the gap between the radiation electrodes is efficiently used to provide an integral RF circuit. Accordingly, even if an integral RF circuit is disposed on a dielectric base, an increase in the size of the dielectric base is prevented thereby preventing any increase in cost.
Furthermore, because an integral RF circuit is disposed on a dielectric base of an antenna, the RF circuit need not be provided on a circuit board of a communication apparatus, allowing the circuit board to be made smaller, thereby facilitating reduction in the size of the communication apparatus.
Furthermore, because radiation electrodes and RF circuits are disposed on the same surface and disposed in proximity to each other, conduction paths for signals between the radiation electrodes and the RF circuits are extremely short, thereby significantly reducing conduction loss.
Furthermore, according to preferred embodiments of the present invention, because radiation electrodes are disposed on a thick portion of a dielectric base, the radiation electrodes favorably transmit or receive radio waves. Furthermore, because a circuit pattern of an integral RF circuit is disposed on a thin portion of the dielectric base, an electric field of the circuit pattern is confined, thereby reducing radiation loss of the circuit pattern. Due to the effect of reducing radiation loss of the circuit pattern and the effect of reducing conduction loss, loss is significantly reduced in an antenna according to preferred embodiments of the present invention, so that sensitivity for transmission or reception is improved. Accordingly, reliability of communication using an antenna with an integral RF circuit, an antenna module, or a communication apparatus is greatly improved.
Furthermore, in an arrangement in which a plurality of radiation electrodes has different resonant frequencies from each other, isolation between the radiation electrodes is greatly improved.
Furthermore, in an antenna module including an antenna with an integral RF circuit according to preferred embodiments of the present invention, a space formed with a concavity of a dielectric base of the antenna with an integral RF circuit is efficiently used to dispose therein a circuit connected to an integral RF circuit. That is, the circuit is disposed within the antenna. Thus, the circuit within the antenna need not be disposed on a circuit board of a communication apparatus, allowing the circuit board to be made smaller accordingly, further facilitating reduction in the size of the communication apparatus.
In an arrangement in which a through hole is provided or a wiring pattern is disposed on a side surface of a dielectric base of an antenna with an integral RF circuit for connecting an integral RF circuit disposed on a top surface of the dielectric base and a circuit disposed within the antenna, the RF circuit of the antenna and the circuit disposed on a substrate can be conductively connected simply by joining the antenna with an integral RF circuit with the substrate, thereby improving efficiency of assembly. Furthermore, in an arrangement in which a metallic pin is used as connecting member, reliability of connection between an integral RF circuit and a circuit on a substrate is improved.
Other features, elements, advantages and characteristics of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.